1. Field of the Invention
This invention relates to demetalation of hydrocarbonaceous feeds. More particularly, this invention relates to an improved method of noncatalytic demetalation of hydrocarbonaceous fluid feeds using a pressurized guard bed or a heat soak zone upstream from hydroprocessing units.
2. Description of Prior Art
Increasing worldwide demand for petroleum products combined with continuously increasing prices for petroleum and products recovered therefrom, has prompted a renewed interest in the sources of hydrocarbons which are less accessible than crude oil of the Middle East and other countries. Alternative sources of energy have been known for a long time, however, the methods of exploration and processing of these sources have not thus far been economically competitive with the traditional sources of petroleum. However, increasing demand for petroleum products, and the resulting continuous increases in prices thereof, makes it apparent that formerly noncompetitive sources of energy will become competitive in the near future and therefore will supply a substantial amount of our energy needs. One of the more promising sources of hydrocarbons that will be used in the future to supply our growing demand are synthetic hydrocarbonaceous fluids obtained from oil shale, normally solid coal, tar, including tar sands, etc. These hydrocarbonaceous fluids are generally referred to by generic terms, such as "synthetic crude oil" or "synthetic oil fractions." The term hydrocarbonaceous fluids as used herein is not limited to synthetically-derived hydrocarbons. The term refers to hydrocarbon fluids derived from conventional sources, e.g., petroleum, and from the alternative sources of energy, e.g., shale oil, tar sands and coal fluids.
One of the problems encountered in processing the aforementioned hydrocarbonaceous fluids resides in the presence of heavy metal contaminants therein which affect the ease of processing of such fluids into satisfactory sources of energy and into precursors for the synthesis of other desired materials, e.g., plastics, resins, etc. For example, shale oil contains appreciable quantities of iron, selenium and arsenic, which are potential hydrotreating catalysts poisons. Accordingly, such impurities must be removed from shale oil and other sources of hydrocarbons prior to processing the shale oil in unit operations containing catalysts which may be poisoned by the impurities contained therein.
Attempts have been made in prior art to remove such contaminants by means of catalytic or noncatalytic methods. Thus, for example, catalytic methods of removal of arsenic are disclosed in U.S. Pat. Nos. 3,622,498 and 3,496,099, while noncatalytic methods are disclosed in U.S. Pat. No. 2,778,779. In addition, U.S. Pat. No. 4,029,571 discloses the thermal "heat soak" demetalation method, whereby arsenic and heavy metal contaminants are precipitated from shale oil in the presence of hydrogen, with or without the use of a separate hydrogenation step. A similar process is also disclosed by Sullivan et al in Catalytic Hydroprocessing of Shale Oil to Produce Distillate Fuels, ADVANCES IN CHEMISTRY, Vol. 179, pages 25-51 (1979). The entire contents of all of the aforementioned patents and publications are incorporated herein by reference.
However, the prior art methods of removing heavy metal and other contaminants from shale oil and other hydrocarbonaceous fluids have met only with partial success because a substantial portion of contaminants remained in the hydrocarbonaceous fluid feeds.
Accordingly, it is the primary object of the present invention to provide an improved process for the removal of heavy metals and other contaminants from hydrocarbonaceous fluid feed streams.
It is an additional object of the present invention to provide an improved non-catalytic process for removing heavy metals contaminants from shale oil.
Additional objects of this invention will become apparent to those skilled in the art from the study of the specification and the appended claims.